The thickness of substrates in semiconductor devices can affect the forward voltage needed to operate the devices at a given current level. In some applications, the performance and/or operation of devices such as SiC Schottky diodes, MOSFETs, MESFETs, BJTs, PiN diodes, n-channel IGBTs, thyristors, vertical JFETs, GaN HEMTS, and/or light emitting diodes (LEDs), etc. may be affected by the relatively high resistance of thick substrates. For example, n-type, 4H-SiC substrates may account for about 1 mohm-cm2 of the specific on-resistance of various devices. This may constitute about 50% of the on-resistance of a 600 V SiC Schottky diode, and/or about 90% of the on-resistance of a 300V SiC Schottky diode. A p-type 4H-SiC substrate may add about 50-100 mohm-cm2 to the device on-resistance. For this reason, it has not been practical to develop vertical devices, such as GTOs and n-channel IGBTs, on p-type SiC substrates. As such, it is sometimes desirable to reduce the thickness of a substrate on which a device is provided. In the case of monolithic microwave integrated circuits (MMICs), such as GaN HEMT and/or SiC MMICs, the substrate thickness may be thinned to control transmission line impedance by allowing the use of viaholes that may provide a low impedance ground connection to the frontside of the device. Reducing the thickness of a substrate is discussed, for example, in U.S. Pat. No. 7,547,578, the disclosure of which is incorporated herein by reference in its entirety.
Present device fabrication technology for reducing the thickness of a substrate typically employs mounting a substrate with devices thereon to a carrier substrate for support and then etching, polishing, or grinding the substrate. In some processing steps, the removal of the carrier substrate may introduce unwanted strain to the reduced thickness substrate and cracks may be introduced within the substrate that propagate and damage the devices located thereon. Cracks may also be introduced in other processing steps, such as device singulation.